1. Field of the Invention
The present invention relates to an image display element for use in a large size display including, for example, a large number of liquid crystal display (LCD) panels, plasma display panels (PDP), or electroluminescent (EL) display panels, arranged therein, and a manufacturing method thereof.
2. Background Art
In recent years, the mainstream of large size displays has been of the system in which a large number of LEDs are arranged. Such a large size display of the LED system increases in arrangement density of LEDs with an increase in resolution, resulting in a high cost. On the other hand, in order to implement a large size display at a low cost, effective is the system in which a plurality of flat panel displays (e.g., LCD panels, PDPs, or EL display panels) as image display elements (or, display units) are arranged in a matrix.
A conventional image display element forming such a large size display has a front panel and a back panel formed of a glass plate or the like as shown in JP-A-2008-191502. The front panel and the back panel are opposed each other with a prescribed distance therebetween, between which a plurality of pixels, and a plurality of electrodes for controlling them are arranged to form a light emitting layer (or a liquid crystal layer). Thus, the periphery thereof is sealed with a seal part. A plurality of the electrodes are applied with control signals including a scanning signal and a data signal from a driving control circuit disposed on the back side of the image display element. As the electrode lead-out systems for applying control signals to the electrodes, there are an end face lead-out system in which a step part is disposed at the periphery of the image display element, namely, at each joint part between the adjacent image display elements, so that electrode lead lines are connected to the electrode terminals at the step part (FIG. 3 of JP-A-2008-191502); and a center lead-out system in which the back panel is divided, and a groove part is disposed at the central part, and electrode lead lines are disposed at electrode terminals disposed at the groove part (FIG. 1 of JP-A-2008-191502).
In the case where a large number of such image display elements are arranged, when the spacing between the pixels of the adjacent image display elements at the joint part is larger than the spacing between pixels in the same image display element, the joint part becomes noticeable.
Thus, with the foregoing end face lead-out system, it is necessary to form the step part of the end part as thin as possible with a high precision. Whereas, with the center lead-out system, the spacing between pixels in the same image display element can be more shortened as compared with the end face lead-out system. However, the groove part is still required to be formed as narrow as possible with a high precision.
Thus, the end face lead-out system has an effect capable of leading out electrodes from the end part of the panel with ease. However, a problem is encountered in the panel shape in the vicinity of the terminal part for disposing the electrode lead line thereon, so that lead-out processing of electrodes becomes difficult. Examples of the electrode lead-out processing method include soldering, wire bonding, and connection by a conductive paste. However, at the step part in the vicinity of the terminal part occurring according to the thickness of the back panel, jigs and tools such as needles and heads for electrode lead-out processing (which will be hereinafter referred to as processing tools) become less likely to reach the terminal part situated at the recesses of the step part.
Further, with the center lead-out system, the lead line of the electrode is led out from the groove part formed at the back panel. Therefore, this configuration is effective as the structure for making the joint parts of the image display elements less noticeable. However, at the groove part in the vicinity of the terminal part occurring according to the thickness of the back panel, the processing tools are still less likely to reach the terminal part situated at the recesses of the groove part. Particularly, a large size display decreases in pixel pitch with an increase in resolution. However, it is also necessary to narrow the width of the terminal part for disposing an electrode lead line thereon according to the decrease in pixel pitch. Accordingly, electrode lead-out processing becomes further difficult. Thus, with the structure of a conventional image display element, it has been difficult to implement a high-resolution large size display by a decrease in gap between pixels when panels are arranged.